Voltage drop along the main power supply and return wires of loads located remotely from a power source interferes with regulating the desired voltage. It is well known that the output voltage of a power source which is feeding a high current load located remotely from the power source may be regulated utilizing feedback signals indicative of the voltage at the load, provided to the power source regulator by means of remote sense leads, rather than using the voltage at the immediate output of the power source. In U.S. Pat. No. 3,818,274, the voltage at the remote load is utilized as a feedback for comparison with a commanded voltage from a computer; the same remote load voltage is utilized to clamp the power amplifier so that it cannot give an excessive overvoltage or undervoltage, regardless of how the computer attempts to drive the output power. However, if the sense lead is broken, the output power will be driven further in whichever polarity the source is attempting to regulate, the overvoltage cannot be detected since the sense lead is broken, and thus the clamp circuit will do no good. In U.S. Pat. No. 4,551,668, detectors are provided to determine if either the sense lead or the sense return lead are broken, and operate an alarm in such case. However, the alarm does not alter the circuit operation, and therefore intermittent breaks will simply cause the alarm to cycle on and off. Furthermore, the connection of the remote sense and sense return lines at the voltage regulation circuit is polarity sensitive, and reversing the polarity of the sense and sense return lines at the input to the voltage regulator will cause the voltage regulator to attempt to drive the load into an overvoltage condition, thereby damaging the power source or the load, or both. In addition, the detector itself is polarity sensitive in the aforesaid '668 patent. Thus, if the sense and sense return lines are reversed when connected, the broken lead detectors will not work.
U.S. Pat. No. 5,117,174 discloses a variable speed, constant frequency aircraft generator system which has a remote voltage regulator sensing voltage at the remote loads for controlling the engine driven power source. It utilizes the power source output voltage at the power source to regulate the voltage of the power source, and utilizes a remote voltage regulator to provide signals from which a trim bias is generated to bias the local voltage regulator in a manner to overcome any losses in the lines feeding the loads. However, this system is useless except where the remote voltage regulator is already in place, and furthermore, it will provide no trim signal in the event that either of the sense leads are broken.